A number of catalysts are known for the conversion of syngas, a mixture of carbon monoxide, carbon dioxide and hydrogen, to alcohols. For the production of alcohols other than methanol, an obstacle in making the conversion process economically viable is the conversion selectivity of the catalyst. Ethanol is a desirable product for use as a fuel additive but it is not efficiently produced by some of the known catalysts.
A first group of catalysts, the promoted methanol catalysts, usually contain copper oxide or zinc and an alkali metal promoter such as potassium or cesium. These catalysts have high selectivity to methanol and isobutanol and produce very little hydrocarbons. A second class of catalysts include copper and cobalt or other Group VIII metals such as iron. They produce primarily mixtures of methanol, ethanol and propanol, but usually also have high selectivity to hydrocarbons. A third class of catalysts contains molybdenum sulphide as the main component. Selectivity to methanol can be reduced significantly, but again the selectivity for hydrocarbons is high.